Summary of Significant Accounting Policies - Goodwill and Other Indefinite-Lived Intangible Assets (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) segment item	Dec. 31, 2018 USD ($) item segment	Dec. 31, 2017 USD ($) segment item
Goodwill and Other Indefinite-Lived Intangible Assets
Number of operating segments \| segment	1	1	1
Number of reportable segments \| item	1	1	1
Impairment of goodwill	$ 0.0	$ 0.0	$ 0.0
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)		$ 16.5

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
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-URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13854-109267

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
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-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13777-109266

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration